public class ComparableCircle extends Circle
  implements Comparable<ComparableCircle> {

  public ComparableCircle() {
  }

  public ComparableCircle(double radius) {
    super(radius);
  }

  @Override
  public int compareTo(ComparableCircle o) {
    if (getArea() > o.getArea()) {
      return 1;
    } else if (getArea() < o.getArea()) {
      return -1;
    }
    return 0;
  }
}
